class_docstr: Atari 2600 preprocessing wrapper.
  
  This class follows the guidelines in Machado et al. (2018),
  "Revisiting the Arcade Learning Environment: Evaluation Protocols and Open Problems for General Agents".
  
  Specifically, the following preprocess stages applies to the atari environment:
  - Noop Reset: Obtains the initial state by taking a random number of no-ops on reset, default max 30 no-ops.
  - Frame skipping: The number of frames skipped between steps, 4 by default
  - Max-pooling: Pools over the most recent two observations from the frame skips
  - Termination signal when a life is lost: When the agent losses a life during the environment, then the environment is terminated.
      Turned off by default. Not recommended by Machado et al. (2018).
  - Resize to a square image: Resizes the atari environment original observation shape from 210x180 to 84x84 by default
  - Grayscale observation: If the observation is colour or greyscale, by default, greyscale.
  - Scale observation: If to scale the observation between [0, 1) or [0, 255), by default, not scaled.
code: def _get_obs(self):
      if self.frame_skip > 1:  # more efficient in-place pooling
          np.maximum(
              self.obs_buffer[0],
              self.obs_buffer[1],
              out=self.obs_buffer[0],
          )
      assert cv2 is not None
      obs = cv2.resize(
          self.obs_buffer[0],
          (self.screen_size, self.screen_size),
          interpolation=cv2.INTER_AREA,
      )
  
      if self.scale_obs:
          obs = np.asarray(obs, dtype=np.float32) / 255.0
      else:
          obs = np.asarray(obs, dtype=np.uint8)
  
      if self.grayscale_obs and self.grayscale_newaxis:
          obs = np.expand_dims(obs, axis=-1)  # Add a channel axis
      return obs
  
file_path: gym/gym/wrappers/atari_preprocessing.py
imports: import numpy
  import gym
  from gym.spaces import Box
label_desc: Use image node_id 5 for calling the AtariPreprocessing obj's underlying member method code with example usage: obj._get_obs() and returns: obs